U.S. Pat. No. 8,696,263 discloses a double sided indexable fast, or high-feed insert which includes four cutting portions. The insert has opposite main surfaces and a peripheral surface which extends therebetween. The peripheral surface includes exactly two large parallel side abutment surfaces located on opposite sides of the clamping bore. The insert also has two pairs of front abutment surfaces, each pair converging outwardly away from the clamping bore. Each cutting portion extends close to a maximum width of the insert defined by the side abutment surface. This so-called slim designed insert will be referred to herein as a “non-winged high-feed insert”.
U.S. Pat. No. 8,950,984 discloses a similar double-sided indexable high-feed insert which, in the context of the current invention—has an improved design over the above-mentioned non-winged insert. Specifically, at the cutting portions the insert in U.S. Pat. No. 8,950,984 has extensions/wings, or enlarged cutting edge portions which protrude outwardly from the insert's sides, increasing the cutting edge length while maintaining the same lead angle. This increases at least cutting depth and ramping angles. This insert will be referred to herein as a “winged high-feed insert”. Nonetheless, this design maintains the two parallel straight side abutment surfaces, and therefore, between the cutting portions, the insert has a narrow portion which extends, or spans across a major portion of the insert's entire longitudinal length. Furthermore, in order to balance said advantages with unwanted breakage of the winged extensions, their length must be optimized, and relatively minimal.
Attention is drawn to FIGS. 1A-1C, which shows a sort of ‘geometry evolution’ of the inserts of the field, drawn to the same scale. FIG. 1A shows a prior art ‘non-winged’ insert geometry, which is similar to the insert geometry disclosed by U.S. Pat. No. 8,696,263. FIG. 1B shows a prior art ‘winged insert geometry, which is similar to the insert geometry disclosed by U.S. Pat. No. 8,950,984. FIG. 1C shows what will be referred to herein as a ‘tapered-waist’ insert geometry according to the subject matter of the present application.
The so-called ‘tapered-waist’ shaped insert geometry of the current invention overcomes the aforementioned disadvantages and provides an advantageous, more robust insert which outperforms the prior art winged and non-winged insert geometries in terms of tool/insert life expectancy, depth of cut at same lead angles, plunging depth, tool ramping angles and in abutment stability in the pocket.